Gear pump and thrust plate therefor



Jan. 16, 1968 R. SISSON GEAR PUMP AND THRUST PLATE THEREFOR 3Sheets-Sheet 1 Filed Dec. 21, 1966 I "IINVENTOR RONALD L. SISSON BY Jan.16, 1968 R. SISSON 3,363,578

GEAR PUMP AND THRUST PLATE THEREFOR Filed Dec. 21, 1966 s sheets-sheet 2FIG. 2

INVENTOR RONALD SISSON ATTORNEY Jan. 16, 1968 R. L. S SSQN 3,363,578

GEAR PUMP AND THRUST PLATE THEREFOR Filed Dec. 21, 1966 3 Sheets-Sheet 3l L f 88 9O 84 58 74 82 INVENTOR RONALD L. SISSON ATTORNEY United StatesPatent 3,363,578 GEAR PUMP AND THRUST PLATE THEREFOR Ronald L. Sisson,Jackson, Mich, assignor to (Ilark Equipment Company, a corporation ofMichigan Filed Dec. 21, 1966, Ser. No. 603,468 16 Claims. (Cl. 103-126)ABSTRACT OF THE DISCLOSURE Thrust plate for a gear pump having aninternal pressure cavity receiving pumped liquid, and a movable plateactuated by pressure of the liquid in the pressure cavity for engagingand sealing the gears, and including resilient means for sealing theplate.

Cross references In the copending application of Sisson and Shreve Ser.No. 603,467, filed Dec. 21, 1966, there is disclosed and claimed athrust plate with a single continuous internal cavity, which is utilizedin the present invention, that applieation being assigned to theassignee of the present application; that application makes reference tocertain prior US. patents also assigned to the assignee of the presentapplication; attention is also directed to another US. patent, No.2,809,592, dated Oct. 15, 1957, to Miller et al.

Disclosure The problems involved in sealing the gears in a gear pumphave been given a great deal of consideration. Thrust plates have beendesigned for seal-ing the gears and more specifically for applyingpressure thereto in certain predetermined areas according to ditferentpressures of the liquid being pumped whereby to produce effectivesealing action at all parts of the gears.

The present invention is directed to that main problem and includes athrust plate construction having an internal pressure cavity forreceiving pumped liquid for producing the desired pressures forimpressing on the gears in the manner stated, i.e., impressing thosepressures in certain predetermined areas on the gears. The constructionincludes a wear plate directly engaging the gears and movable inresponse to variation in pressures of the liquid in the internalpressure cavity. The pressure plate is flexible for producing thedesired distribution of pressures upon the gears and it is desired toseal the spaces between the wear plate and the other elements of thethrust plate.

It is therefore a main object of the present invention to provide athrust plate of the foregoing general character including a novelarrangement for sealing the wear plate relative to the remainder of theconstruction of the thrust plate.

Another object is to provide a construction of the character justreferred to in which the sealing means is resilient and the remainder ofthe thrust plate is arranged so as to prevent the extrusion of theresilient sealing means into the spaces between other elements of thethrust plate.

A still more specific object is to provide a thrust plate of theforegoing general character in which a novel arrangement is provided fordirecting the pressure of the liquid in the pressure cavity against theresilient sealing means most effectively for producing the desiredsealing effect between the wear plate and other elements of the thrustplate.

A still further object is to provide a completely unitary andself-contained thrust plate of novel construction.

Still another object is to provide novel gear pump constructionincorporating a thrust plate of the foregoing general character.

Other objects and advantages of the invention will appear from thefollowing detail description taken in conjunction with the accompanyingdrawings in which:

FIGURE 1 is a sectional view of a gear pump incorporating the thrustplate of the present invention, the section being taken in the planecontaining the axes of the gears of the pump;

FIGURE 2 is an end view taken from the left of FIG- URE 1 with the nearhousing cover assembly removed and exposing the thrust plate of theinvention, the thrust plate being viewed from the plane of the line 22of FIG- URE 1;

FIGURE 3 is a face view of the thrust plate from the side opposite thatshown in FIGURE 2, and on an enlarged scale, being oriented according tothe plane of the line 33 of FIGURE 1;

FIGURE 4 is a sectional view taken at line 44 of FIGURE 3; and

FIGURE 5 is a setcional view taken at line 5-5 of FIGURE 3.

Referring in detail to the drawings, the gear pump incorporating thethrust plate of the present invention is shown in FIGURE 1 and indicatedin its entirety at 10 and includes a housing 12 made up of a centralhousing member 14, a front cover assembly 16 and a rear cover assembly18. The pump includes a driving gear 20 and a driven gear 22intermeshing therewith, in chambers 24 and 26. The driving gear 20 hasshaft elements, preferably integral therewith, 28 and 3t? journalled insuitable bearings 32. It also includes a shaft extension 34 adapted forconnection with a driving means. The driven gear 22 has shaft elements36 and 38, also preferably integral, journalled in suitable bearings 40.The housing sections may be sealed by suitable gaskets 42 while theshaft extension 34 may be sealed by conventional sealing means 44. Thehousing also defines an inlet passage 46 (FIGURE 2) and an outletpassage 48.

A fixed thrust plate 50 of suitable construction is interposed betweenthe gears and the inner face 51 of the rear cover assembly 18 receivingthe thrust from the gears provided by a semi-rigid thrust plate, orthrust plate means or construction 52, comprising the principal featureof the invention. The positioning of the thrust plate 52 and its detailconstruction are described hereinbelow.

The thrust plate 52 is constructed for applying pressures against thegears axially thereof in the areas affected by the positive pressures inthe liquid being pumped, these latter pressures being exemplified in thegear teeth pockets in different amounts between the outlet passage andinlet passage, as is known.

The thrust plate is disposed in a recess 53 formed in the front coverassembly 16 provided for the purpose, being confined between the gearsand the inner surface 54 of the recess, this surface being the effectiveopposed surface of the front cover assembly 16. The recess 53 has anouter surrounding Wall surface 55. The thrust plate includes a wearplate controlled by the pressure in the internal cavity of the thrustplate, this internal cavity being generally similar to that disclosedand claimed broadly in the copending application referred to above.

Referring to the specific and detail construction of the thrust plate,it includes a rigid backing plate 56 of die cast aluminum or formedsteel, for example, having a main planar or flat plate element 58 and apair of apertures 69 for receiving the shaft elements of the gears,these apertures being surrounded by cylindrical flanges 62 extendingperpendicular to the plate element 58 and extending nearly the fulldepth dimension of the thrust plate. The backing plate also has anopening 64 surrounded by a flange 66 perpendicular to the plate element58, this opening communicating with the inlet passage 46 of the pump, inthe assembly of the thrust plate in the pump.

Opposed to the backing plate 56 is a flexible wear plate 68substantially coterminous with the plate element 58 and having aperturesreceiving the flanges 62 and another aperture 72 receiving the flange64, all in snug but sliding engagement with the flanges. The wear plate68 is in planar form and disposed parallel to the plate element 58 ofthe backing plate, defining a pressure cavity 74 therewith. The pressureplate 68 is provided with an aperture 76 for establishing communicationbetween the outlet passage 48 and the pressure cavity 74. The outersurfaces of the flanges 62 and 66 are swaged to provide line contactengagement and zero clearance with the marginal edges of the apertures70 and 72.

Surrounding the backing plate 56 and wear plate 68, and forming a partof the thrust plate, is a gasket 78, of T- shape cross section having across-bar element 86 entirely surrounding the plates and engaging theouter marginal edges thereof, the gasket being dimensioned forself-biasing inwardly in snug engagement therewith. The gasket includesan inwardly extending element 82 positioned between the plates and whichcan be dimensioned for snug engagement therewith and initial biasing ofthem apart for producing a pre-loading effect on the wear plate. Thegasket 78 of rubber or rubber-like material, may be of one piece, thevarious elements referred to being all integral and positioned andshaped and dimensioned for cooperating with the elements of the backingplate and Wear plate as mentioned. The gasket 78 includes elements 84surrounding the flanges 62 of the apertures 60, while a portion 82a ofthe element 82 extends along the flange 66 of the aperture 64. Thegasket elements 84 also can be dimensioned for providing a pre-loadingeffect on the wear plate. However it is not necessary to provide suchpre-loading effect by the gasket elements 82 and 84.

The elements 84 and 82a of the gasket are provided with a single groove88 in their under surface (FIGURES 4 and 5), i.e., the surface facingthe element 58 of the backing plate. This groove preferably iscontinuous around each of the flanges 62 as Well as around the flange66, receiving liquid from the pressure cavity 74 into which the liquidis transmitted from the outlet passage of the pump. The communicationbetween the pressure cavity 74 and the groove 88 is provided by a notch90 formed in the rib defining one side of the groove. The groove 88includes segments 88a surrounding the flanges 62 and another segment88!; extending along one side and the ends of the flange 66. In thisarea, the groove segment 88b is formed in a portion 82a of the gasketelement 82.

The liquid in the pressure cavity 74 enters into the groove 88 andcompletely fills it around all of the apertures, and upon increase ofthe pressure of the liquid in the pressure cavity 74, that pressure isexerted in the groove against the gasket and thereby against the wearplate 68, and perpendicular thereto. The wear plate is devoid ofrestrictive mechanical connection with the backing plate free floatingrelative thereto. The elements 84 surrounding the apertures 60 and theelement 82a are also provided with another groove 92 preferably ofrectangular shape and relatively flat in which is disposed a gasket 94of relatively non-resilient fiber material directly engaging the innersurface of the wear plate 68.

The thrust plate 52 is positioned in the recess 53 (FIG- URE 1) with thebacking plate 56 engaging the surface 54 and the wear plate 68 directlyengaging the gears. Preferably the recess is of greater dimensions thanthe chambers 24, 26 and the thrust plate similarly dimensioned so thatthe wear plate 68 engages the surface 96 of the central housing member14. The apertures 60 are also appropriately dimensioned so that the wearplate, around the gear shaft elements, extends radially inwardly beyondthe gear teeth to correspondingly engage the hubs of the gears andthereby seal the gear chambers.

The aperture 64 is in constant communication with the inlet chamber 46while the small aperture 76 is in constant engagement with the outletpassage, and the pumped liquid therein under positive pressure is forcedthrough the aperture 76 into the pressure cavity 74. This increasedpressure in the pressure cavity forces the wear plate 68 outwardlyagainst the gears and the surface 96 of the central housing section andin doing so Works against the various elements of the gasket 78. In thecase of the outer peripheral portion of the gasket, the liquid worksagainst the radially inwardly extending element 82 and biases orcompresses the gasket outwardly into sealing engagement with theperipheral wall 55 of the recess 53, this compressing action on thegasket also spreading the element 82 in axial direction, maintaining asealing engagement between the gasket and the Wear plate and backingplate. The liquid under pressure in the pressure cavity 74 also worksagainst the gasket elements 84 and compresses them radiallyinwardly'against the flanges 62 and 66 and it also works in the groove88 and against the gasket, forcing the latter axially against the wearplate. In this action, the more rigid fiber gasket 92 directly engagesthe wear plate and in addition to its liquid scaling function, itprovides a direct Wear-resistant and body-maintaining function in thecompression of the gasket against the Wear plate 68 and insulatesagainst heat.

The line-contact engagement and zero clearance between the marginaledges of the apertures 70 and 72 in the wear plate and flanges 62 and 66prevents the extrusion of any of the elements of the gasket therebetweenand in fact provides a relatively effective seal in itself so that thefiber gasket 92 is actually not necessary.

An advantage of the invention is that the thrust plate can be used in acast-iron pump housing where a loading area for receiving the thrustplate otherwise would entail an expensive machining operation. Thethrust plate would similarly enable a loading area change withoutaffecting the pump housing, since the wear plate would readily adapt toa flat-fitting position against the gears despite any irregularities inthe front cover assembly or in the backing plate.

Additionally the thrust plate may be used in connection with differentkinds of bearings, (such as 32, 40 FIGURE 1) regardless of the characterof those bearings, e.g., whether sleeve bearing, roller bearing, etc.,and regardless of the diameter of those bearings Within wide limits.

The zero clearance produced by the sw-aging operation around the flangesprovides a longer life of a resilient gasket, and in fact resilientsealing means is not actually required around the apertures 60 and 64.

The initial tolerances required in the stamped apertures 70, 72 in thewear plate are not critical because the swaging operation performedprovides the desired zero clearance regardless of inaccuracies in theoriginal formation of those apertures.

The edges defining the apertures 70, 72 remain in engagement with thesurfaces of the flanges 62, 66 at all times throughout the range ofmovement of the wear plate away from and toward the backing plate, i.e.,the wear plate does not move off of or beyond the flanges since the wearplate is substantially thicker than the great est extent of its movementso that at no time is there a condition in which an opening exists insuch direction that the gasket could spread or extrude transverselyi.e., in the direction of the plane of the thrust plate.

The thrust plate is completely unitary and self-contained, not requiringcooperation of any element of the pump housing to complete itsstructure.

While I have herein disclosed a preferred form of the invention, it willbe understood that changes may be made therein within the spirit andscope of the appended claims.

I claim:

1. A thrust plate for a gear pump comprising a backing plate having anaperture and a flange surrounding the aperture, a wear plate fitted tothe backing plate in spaced relation thereto and forming a pressurecavity therebetween, the wear plate having an aperture receiving saidflange, and resilient gasket means between the backing plate and wearplate sealing the pressure cavity, the gasket means including an elementsurrounding said flange and butting the wear plate and having suchconformation that liquid under pressure in the pressure cavity forcesthe gasket perpendicularly into sealing engagement with the wear plate.

2. The invention set out in claim 1 wherein said gasket elementsurrounding the flange has a groove on the side thereof facing thebacking plate and an opening communicating between the groove and theinterior of the pressure cavity, the groove thereby being so locatedthat liquid in the groove operates to force the gasket element in thedirection stated.

3. The invention set out in claim 1 wherein said wear plate possesses atleast a degree of flexibility.

4. The invention set out in claim 3 wherein the thrust plate is adaptedfor use in a space in which the movement of the wear plate toward andfrom the backing plate is extremely small, and the correspondingmovement of the gasket element in that direction is complementallysmall, and the thickness of the wear plate is substantially greater thansaid small amount of movement, whereby the flange always remainsprojected into the aperture in the wear plate.

5. The invention set out in claim 1 wherein the aperture in the wearplate and the outer surface of the flange are so relatively shaped anddimensioned that substantially line-contact engagement, and zeroclearance, are established therebetween.

6. The invention set out in claim 1 wherein said gasket element isprovided with a groove on the side thereof facing the wear plate, and asubstantially non-resilient fiber gasket is interposed in said groove,in engagement with both the wear plate and flange overlying the openingtherebetween.

7. The invention set out in claim 1 wherein the gasket means includes anouter element extending around the outer peripheral edges of the backingplate and wear plate and surrounding and defining the outer edges ofsaid pressure cavity, and forming a liquid seal between the backingplate and pressure plate.

8. The invention set out in claim 7 wherein said outer gasket elementhas a laterally outward exposed sealing surface continuously around thethrust plate for sealing engagement with a surrounding wall surfaceextending generally transverse to the planes of the backing plate andwear plate.

9. The invention set out in claim 8 wherein said outer gasket element issubstantially T-shape in cross section having an outer element formingsaid outwardly exposed sealing surface and another element extendinglaterally inwardly between the backing plate and wear plate.

10. The invention set out in claim 1 wherein said aperture in thebacking plate is one of a pair of apertures for receiving gear elementsand the thrust plate includes a third aperture adjacent one edgethereof, and the backing plate includes flanges surrounding all of theapertures, the gasket means is a single integral member having anelement surrounding each of the flanges and dimensioned for constantlyproducing an inwardly biasing effect, in sealing engagement with thoseflanges, said elements together having a continuous groove in the sidethereof facing the backing plate, the gasket means having a notchforming a passage communicating between the pressure cavity and thegroove, said gasket elements having such dimensions as to produce aconstant biasing effect against the wear plate substantiallyperpendicular thereto for providing a preloaded condition thereon, andthe gasket means including outer surrounding element substantiallyT-shape in cross section including an outer cross bar element providinga surrounding sealing surface substantially perpendicular to the thrustplate for engagement with a surrounding wall surface, said outer gasketelement also including an inwardly directed extension between thebacking plate and wear plate dimensioned so as to produce a constantbiasing effect on the wear plate and producing a preloaded conditionthereon, said wear plate having an aperture therethrough communicatingwith the pressure cavity.

11. For use in a gear pump having gears and a cover assembly having arecess facing the gears, a thrust plate of unitary and self-containedconstruction adapted to be placed in the recess, and including a backingplate and a wear plate of similar outline size and shape arranged inopposed relation with a space therebetween, the wear plate beingdetached from the back plate and freely bodily movable toward and fromthe backing plate, and sealing means mounted on and carried by thebacking plate and wear plate and together therewith forming a singlepressure cavity of said space and also completing the thrust plate, thesealing means having an element surrounding the backing plate and wearplate, such unitary thrust plate constituting the sole means, exceptelements of the gears, in the recess and the sole means reacting betweenthe surfaces of the recess and the gears.

12. The invention set out in claim 11 wherein the wear plate is of rigidconstruction and of planar shape whereby to be enabled to fit flatlyagainst the gears.

13. The invention set out in claim 12 wherein the backing plate is alsorigid, whereby to rigidly support the thrust plate as a whole inresponse to the reaction of the thrust plate being forced against thegears.

14. The invention set out in claim 11 wherein the sealing means includesan element entirely surrounding the thrust plate with a laterallyoutwardly exposed sealing surface adapted for sealing engagement withthe surrounding wall surface of the recess.

15. The invention set out in claim 11 in conjunction with said gearpump, the thrust plate being removably disposed in the recess and thewear plate engaging the gears, and the surrounding element of thesealing means sealingly engaging the surrounding surface of the recessentirely threrearound.

16. The invention set out in claim 15 wherein the wear plate is of rigidcharacter, devoid of restrictive mechanical connection with the backingplate and free floating relative thereto for full engagement with thegears throughout the end area of the gears.

References Cited UNITED STATES PATENTS 2,809,592 10/1957 Miller et a1103-126 2,816,512 12/ 1957 Murray 103-126 2,853,952 9/1958 Aspelin103-126 2,967,487 1/ 1961 Nagely 103-126 3,050,010 8/1962 Thrap et a1.103-126 3,096,719 7/1963 McAlvay 103-126 3,101,673 8/1963 Clark et al.103-126 3,131,643 5/1964 Marietta 103-126 3,137,238 6/1964 Gordon103-126 3,174,435 3/1965 Sisson et al. 103-126 3,213,799 10/1965 Trick103-126 3,294,029 12/ 1966 Clark et al. 103-126 DONLEY J. STOCKING,Primary Examiner. WILBUR I. GOODLIN, Examiner.

